On Sun, 18 Sep 2022 09:50:58 +0100, Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> wrote: > > On 17/09/2022 19:47, Marc Zyngier wrote: > > On Sat, 17 Sep 2022 17:51:20 +0100, > > Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> wrote: > >> > >> On 16/09/2022 14:30, Jean-Philippe Brucker wrote: > >>> QEMU uses both "arm,armv8-timer" and "arm,armv7-timer" as compatible > >>> string. Although it is unlikely that any guest relies on this, we can't > >>> be certain of that. Therefore, add these to the schema. Clean up the > >>> compatible list a little while at it. > >>> > >>> Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> > >> > >> I guess you wanted to say QEMU uses "arm,armv8-timer" followed by > >> "arm,armv7-timer", because otherwise I would understand it that either > >> that or that. Anyway, is it a valid (virtualized) hardware? Is ARMv8 > >> timer really, really compatible with ARMv7 one? > > > > Yes. There isn't a shred of difference between the two in the earlier > > revisions of the ARMv8 architecture, and none of the differences > > introduced in later revisions are exposed to DT anyway. > > > >> I don't think we should document invalid setups out-of-tree, just > >> because they are there, and something like this was also expressed by Rob: > >> https://lore.kernel.org/all/20220518163255.GE3302100-robh@xxxxxxxxxx/ > > > > This is, on the contrary, something that is perfectly valid. For > > example, a system running a 32bit OS on a 64bit system is perfectly > > entitled to expose both (v8 because that's what the HW is, v7 because > > that's what the OS is the most likely to understand). > > > > You may find it odd, but that: > > > > - expresses something that is actually required > > > > - is what I, as the original author of this binding, have always > > considered valid > > > > - has been valid for a long time (10+ years) before you decided it > > suddenly wasn't > > > > I understand that the "DT police" has high standards, but this has > > been around for much longer, and it isn't because the conversion to > > schema is imperfect that you can rewrite history. > > > > As for the patch, I'd remove the QEMU reference and the deprecation. > > This format is perfectly allowed, and is in use in most VMMs out > > there. Yes, DT is an ABI. > > Thanks for the explanation, actually enough was to say that it is > perfectly valid combination describing hardware. :) Assuming that the original posting was wrong without understanding the context is what triggered it. It is absolutely fine not to know these things, but in this case *do ask questions* rather than dismiss the patch off the bat based of third hand conclusions. Now at least you have the full picture. M. -- Without deviation from the norm, progress is not possible.
